The present invention relates generally to multi-speaker sound reproduction systems, and more particularly to a fader circuit for selectively attenuating audio signals produced by individual speakers in such a system.
Stereophonic sound reproduction systems, particularly those intended for use in automobiles, frequently include two or more individual loudspeakers in each audio channel. For example, it is a common practice to locate one loudspeaker in each of the four corners of an automobile passenger compartment. By selectively attenuating the sound reproduced by the front and rear pair of speakers, the apparent source of reproduced sound can be shifted, thereby permitting the system to be adjusted to suit the particular desires of the front and rear seat passengers.
To provide independent variable attenuation of the front and rear speaker signals, multi-speaker sound reproduction systems are typically provided with some form of fader control. One well-known fader control calls for the use of separate amplifiers, each of which drives a single speaker. By independently adjusting the gain of each amplifier, reproduced signals can be selectively attenuated as desired. However, the use of separate amplifiers greatly increases the cost and complexity of the resulting audio system.
Another known fader control technique calls for connecting a pair of speakers to each output of a conventional two-channel stereophonic amplifier. Variable resistors or potentiometers, connected in series with each speaker, add or subtract resistance as needed to achieve the desired attenuation. Since it is required that each resistance be able to dissipate considerable power, the components involved are of necessity bulky, limiting the degree of miniaturization obtainable when the technique is used.
To overcome the deficiencies of prior fader control arrangements, the present invention provides a purely electronic fader control. Mechanically actuate components are eliminated, resulting in improved reliability and compatibility with totally electronic push-button designs is provided. The relatively small space requirements of the fader circuitry permit the construction of miniature units having significantly less distortion than systems relying on variable resistances. Finally, the present invention provides a wider attenuation range than that available under prior systems together with greater manufacturing economy.
In view of the foregoing, it is a general object of the present invention to provide a new and improved multi-speaker sound reproduction system.
It is a more specific object of the present invention to provide a new and improved fader control for multi-speaker sound reproduction systems.
It is a still more specific object of the present invention to provide an electronic fader control for sound reproduction systems.